A field experiment using acoustic alarms (pingers) to reduce harbour porpoise by-catch in bottom-set gillnets

Carlström, Julia; Berggren, Per; Dinnétz, Felicia; Börjesson, Patrik

doi:10.1006/jmsc.2002.1214

Cited by 35 publications

(36 citation statements)

References 13 publications

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“…Extensive use of pingers could thus have significant consequences for the population if they are used in important harbour porpoise habitats (for example, Special Areas of Conservation), which has been suggested previously (e.g. Culik et al 2001, Carlstrøm et al 2002.…”

Section: Habitat Displacementmentioning

confidence: 84%

Pingers cause temporary habitat displacement in the harbour porpoise Phocoena phocoena

Kyhn¹,

Jørgensen²,

Carstensen³

et al. 2015

Mar. Ecol. Prog. Ser.

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Several studies have shown that pingers mitigate porpoise bycatch and thus pinger use is now mandatory in some fisheries -although the long-term effects of pinger exposure on porpoises have not been well studied. The effects of 2 types of pingers (Airmar: 10 kHz tone; SaveWave Black Saver: 30−160 kHz sweep) on the presence of wild harbour porpoises, Phocoena phocoena, were investigated in 2 areas. Pinger spacing within the areas was similar to that used in commercial fisheries. Two scenarios were tested: (1) pingers were periodically activated and deactivated during 6 periods resembling the deployment and recovery of nets in a gillnet fishery, and (2) pingers were active continuously for 28 d. Acoustic dataloggers (T-PODs) were deployed, 4 within the pinger areas and 3 in control areas, and detected porpoise echolocation activity throughout the entire study. During the periodic-exposure scenario, the porpoise detection rate was reduced by 56% when pingers were active. The reduction was larger for the SaveWave pingers (65%) than for the Airmar pingers (40%). There was a tendency for the encounter rate to increase after the first 2−4 periodic exposures, which could indicate gradual habituation. During the continuous-exposure scenario, the detection rate was reduced by 65% throughout the 28 d with no sign of habituation. In the control areas (2.5, 3 and 5 km distant), neither a decrease nor an increase in detection rate was observed, suggesting that porpoises were displaced either < 2.5 km or > 5 km away. If pingers are used as deterrent devices, the impact of habitat exclusion must therefore be considered concurrently with mitigation of bycatch, especially when regulating fisheries in Marine Protected Areas.

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Section: Habitat Displacementmentioning

confidence: 84%

Pingers cause temporary habitat displacement in the harbour porpoise Phocoena phocoena

Kyhn¹,

Jørgensen²,

Carstensen³

et al. 2015

Mar. Ecol. Prog. Ser.

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“…To avoid accidental entanglements, active deterrent devices like pingers may be needed. Such devices have already proven very effective in preventing by-catch (Kraus et al 1997, Carlström et al 2002, Larsen et al 2002. …”

Section: Discussionmentioning

confidence: 99%

Swimming patterns of wild harbour porpoises Phocoena phocoena show detection and avoidance of gillnets at very long ranges

Nielsen¹,

Wahlberg²,

Heikkilä³

et al. 2012

Mar. Ecol. Prog. Ser.

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Harbour porpoises Phocoena phocoena are unintentionally caught in gillnets. Although the effectiveness of by-catch mitigation measures has been evaluated many times, only a few studies have investigated the behavioural patterns of the porpoises in relation to the presence of fishing nets. In this study, the reactions of wild harbour porpoises to a modified gillnet were visually observed. The porpoises responded to the net by avoiding it, with reactions being detectable at a distance of >80 m. The number of animals in the pods approaching the net did not affect the behaviour of individuals in relation to the net. These results strongly indicate that porpoises do not usually actively approach gillnets. The by-catch problem seems, therefore, to be caused by individual animals accidentally being caught, likely due to attention shifts or to auditory masking reducing their ability to detect the nets using echolocation. KEY WORDS: Harbour porpoise · Phocoena phocoena · Swimming pattern · By-catch · GillnetResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 453: 241-248, 2012 ( Kastelein et al. 1995a). In an additional study, the swimming patterns of the animals were restricted when ropes were placed diagonally from surface to bottom in the pool (Kastelein et al. 1995b). These studies were both conducted in an extremely small tank and it is therefore difficult to extrapolate their findings to free-swimming animals. A field study (Koschinski et al. 2006) using acoustic data loggers to monitor porpoise be haviour compared the response to a regular fishing net with a net to which barium sulphate had been added to increase its acoustic reflectivity. Although the harbour porpoises seemed to respond to the barium sulphate net at slightly greater distances than the regular net, they also seemed to emit fewer echolocation clicks towards the treated net compared with the regular one (Koschinski et al. 2006). The interpretations of the results are, however, limited by various assumptions that must be made when de ducing animal behaviour from acoustic logger data. These previous studies clearly show that more observations on harbour porpoise gillnet interactions in natural circumstances are needed to better understand the by-catch problem and how it should be mitigated.Several hypotheses have been put forward to explain why harbour porpoises get caught in fishing nets. One states that the animals do not detect the net, or detect it too late to avoid it (Larsen et al. 2007, Mooney et al. 2007, another is that harbour porpoises do detect the net but do not consider it a hazard (Au & Jones 1991, Mooney et al. 2007. In the present study we tested these hypotheses by observing visually how wild harbour porpoises responded to a modified gillnet deployed in their natural habitat. MATERIALS AND METHODS Study areaThe study was conducted off the west coast of the peninsula Fyns Hoved, Denmark (55°37.2' N, 10°35.3' E). The study area was approximately 400 m (north−south) along the coa...

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“…Pingers seem to efficiently reduce the by-catch of marine mammals in different type of fishing gear [21]. For example, they were successfully employed to reduce the by-catch of the shortbeaked common dolphin in the California drift net fishery [21] and to limit porpoise by-catch [19][20][21][22] and baleen whale entrapment in coastal set-nets and traps [23]. However, pinger technology has only rarely been used to study the effect of a pinger on the fishing gear, i.e., the degree to which it reduces damage to the nets, and how it functions in terms of improving the catch [24].…”

Section: Introductionmentioning

confidence: 99%

“…Alternatives have been sought for passive methods, such as making net materials more easily detectable by echolocating animals, [15][16][17]; these include active methods, such as the use of mechanical and electronic sound generators [2,[18][19][20]. Pingers are acoustic deterrent devices based on a relatively low acoustic source level (typically less than 150 dB re 1 lPa at 1 m) and operating from middle to high frequencies (2.5-10 kHz) with harmonics to higher frequencies [7].…”

Section: Introductionmentioning

confidence: 99%

Pinger affects fish catch efficiency and damage to bottom gill nets related to bottlenose dolphins

et al. 2009

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There is some evidence that the presence of Tursiops truncatus in fishing areas represents a real economic threat to fishermen due the dolphin feeding on the entangled fish, damaging the nets and reducing the fish catch. We have carried out experiments to assess the efficiency of a pinger in decreasing the interaction between the dolphins and fishing nets, in a fishing area off the coast of southern Italy, where Tursiops truncatus is frequently observed to interact with bottom gill nets. Two identical monofilament bottom gill nets (900 m long), one equipped with pingers and the other without, were used to measure the effect of these pingers on the abundance of the catch and net damage. For each haul (58 in total), data on dolphin sightings near the nets, damage judged to have been done by dolphins, weight and species composition of the catch were collected. All damage to the nets were recorded at the end of each haul. Dolphins in the fishing area were sighted 11 times out of 29 fishing activities (38%). The net equipped with pingers contained 28% more fish (biomass) than the net without pingers (t test, P \ 0.04) and was less damaged (-31%, t test, P \ 0.01). To assess whether the efficacy of these pingers remain constant over long period, long-term experiments should be carried out.

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A field experiment using acoustic alarms (pingers) to reduce harbour porpoise by-catch in bottom-set gillnets

Cited by 35 publications

References 13 publications

Pingers cause temporary habitat displacement in the harbour porpoise Phocoena phocoena

Pingers cause temporary habitat displacement in the harbour porpoise Phocoena phocoena

Swimming patterns of wild harbour porpoises Phocoena phocoena show detection and avoidance of gillnets at very long ranges

Pinger affects fish catch efficiency and damage to bottom gill nets related to bottlenose dolphins

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